Systemin is the first polypeptide hormone identified in plants, in 1991. Systemin is a small polypeptide hormone that conveys information about insect herbivory systemically (to other tissues). A previous report suggested that the tomato homologue of the brassinosteroid receptor BRI1 serves as a systemin receptor, but this finding has been hard to replicate. Now, starting with introgression lines between cultivated and wild tomato (systemin-responsive and non-responsive, respectively), Wang et al. mapped and identified SYR1 as a high-affinity, high-specificity systemin receptor. When SYR1 was introduced into Arabidopsis or tobacco, it conferred upon them sensitivity to systemin. When introduced into the non-responsive tomato species, it conferred resistance against insect herbivory. These studies demonstrate a role for SYR1 in systemin perception and defense against herbivory. (Summary by Mary Williams) Nature Plants 10.1038/s41477-018-0106-0